Page:Popular Science Monthly Volume 91.djvu/956

 940

��pipe tee-joint, set at an angle of 45 cleg., as shown in Fig. 2. The method is exactly the same as for Fig. 1. Draw the front view A (to get the correct angle follow the method given in the last part of this article on easy method of laying out angle). Draw and

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��This pattern for a round pipe is developed in the same manner as for the other types

number the bottom view C. Lay off the base line D-E and project lines over for the pattern. For the pattern of the horizontal pipe, project the length upward and get the length of the line H-K by stepping off the distances from the end view F. To get the hole G, run the points over from the end view F on the front view A, then upward until they cross the same numbered lines coming from the line H-K.

The method of developing the patterns for the round pipe angle of 90 deg., shown in Fig. 3, is exactly the same as in the square pipe Fig. 1. A larger number of lines must be used in this round pipe than in the square pipe and the method, though the same, may appear more complicated. Draw the front view A and bottom view C. Divide the bottom into 16 parts. Lay off the base line D-E, and step off 16 spaces equal to the spaces on the bottom view. This will give the correct length of the base line. Project lines upwards from the bot- tom view until they strike the joint lines, then project them over to the right until they cross the same numbered lines coming up from the base line D-E. Connect these crossing points with a curved line and you will have the pattern as shown in the drawing.

To develop the pattern for the horizontal pipe, draw the end view B and divide it into 16 parts. Lay off the line H-K the correct length by stepping off sixteen spaces

��from the end view; then draw lines across from these points. From the end view run points 13 and 5 (which are shown as one line on the drawing) over to the front view until they strike the lines 13 and 5 coming up from the bottom view C. Run them up to the pattern until they cross lines 13 and 5 on the pattern. Do the same with the other points. The dotted lines show the half hole on the edge as explained for the drawing Fig. 1. The pattern for round pipe tee-joint having an angle of 45 deg., shown in Fig. 4, is developed in the same way as for the other three joints.

Allowances for lock seams should be made on all these patterns as explained in a previous article.

Easy Method of Laying Out Angles for Tee- Joints

Angles are sometimes laid out by means of an instrument called a protractor, but an easy method is shown in the illustration. A circle, Fig. 5, contains 360 deg.; a half circle contains 180 deg., and a quarter- circle gives an angle of 90 deg. In the circle, Fig. 6, is shown a quarter-circle divided in half, which gives two angles of 45 deg. each; the other quarter-circle is divided into three equal parts, which gives three angles of 30 deg. each. If all of the degrees in the various angles are added to- gether they will total 360 degrees.

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��The plan of development of a pattern for a round pipe is the same as for the square

In the circle, Fig. 7, one quarter of it is divided into three equal parts of 30 deg. each, one of which is divided into two equal parts of 15 deg. each, and the other into three equal parts of 10 deg. each. The other quarter-circle is divided into three

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